Etching and passivation of silicon in alkaline solution: A coupled chemical/electrochemical system

Three types of experiments were used to study the surface chemistry of sili con in alkaline solution: minority carrier injection from a p-n junction el ectrode, in-situ photoluminescence, and electron transfer to a redox system in solution. The results lead to the conclusion that the surface chemistry and electrochemistry are determined to a large extent by an activated inte rmediate of the chemical etching reaction of silicon with water. This novel coupling of chemical and electrochemical steps can account for some unusua l features of the system, such as a mechanism for anodic oxidation and pass ivation based on electron injection and the strong influence of a weak oxid izing agent on the surface morphology of chemically etched silicon.